Brown spotting but positive hpt

Kay

I️ got a faint line on an FRER yesterday at about 11-12 DPO, then last night and when I️ woke up this morning I️ had some brown spotting. I️ figured my period was starting and was disappointed, but decided to take another FRER this morning just for the hell of it. Well the line was darker than it was yesterday...anyone have any insight into this? Is it possible that I’m having a chemical pregnancy?